Re: Pulsar Nav accuracy

----- Original Message -----
From: "B Lin" <lin@rxkinetix.com>
> a) what if you're going to place that doesn't have any signals yet -
i.e.
500LY or more away from Sol?  Even early signals won't have a time stamp
(at
least I don't think the orignal episodes of I Love Lucy don't)

Take old issues of TV guide with you ;-).
Actually, News shows were pretty regular and usually did have a clock
somewhere in the background

> b) Assuming advanced tech drives, non-FTL speeds could reach an
appreciable portion of the speed of light, how do you correct for the
time
shift of the internal chronometers compared to the rest of the universe?
Differences of micro or milli seconds could occur if you stayed at
"high"
velocities long enough.

You can get higher differences than that. But you can compensate for the
relativistic dilation without problems - in principle at least. It just
depends on how well you can track your speeds.

> c) Stars, systems and galaxies are all moving - tens, even hundreds of
thousands of miles per hour which would mean some systems are moving a
few
light-seconds every day away from Sol.	After a year, a decade or even a
century they could be as far 2 light hours per year or 8.3 light days
per
century. You'd have to measure the velocity of the star or system to
correct
for any red-shift (or blue-shift for that matter)in your timing signal. 
The
shift in wavelength might add to the imprecision of the measurements.
These
velocities would be in refrence to Sol, other systems might see a
different
velocity.

The problem is no different, in principle, from tracking the planets in
our
solar system. Know the positions at some point in time, know the
velocities,
masses and gravitational influences, and you can track heavenly bodies
to
your hearts desire. Not that hard, though it gets calculation-intensive
if
you are dealing with many bodies and long timespans. Also there are
limits
to the accuracy, but not something that would really crash the scheme.

It doesn't even take a computer to do it for limited systems. As soon as
the
Kopernikan system became popular, mechanical Orrerys were being
built.And
one of the outer planets (Neptune ?) was discovered by the gravitational
disturbances it caused on the orbits of other planets. The orbital
irregularities of Mercury were calculated from the principles of general
relativity - all before electronic computers.

> d) For a standard map to work, we'd need a good, fixed reference point
to
start from - Are we going to use some sort of Galactic North Pole? or
perhaps a "True Galactic Blackhole Center" at or near the center of the
galaxy?  Does the Tufflyverse have humans getting to the center of the
Galaxy?  Or would we be Sol-centric and make Sol our reference point?

You would do a computer map using coordinates relative to a defined
point in
space-time (say, Sol, 1.Jan.2000 00:00, ), Transforming it to any other
point is a trivial exrecice, as would be to produce star maps showing
how
the sky would look from any point in space time.

> I think that we sometimes forget that we live in a relative world.  If
you
stand at the equator, you don't feel motion, even though you are
traveling
1,000 miles per hour as the earth rotates.  In addition, you are moving
67,0000 miles per hour (+/- a thousand) as the Earth orbits the sun.

And the sun is moving trhough the galaxy

> Since everything around you is moving at the same rate, you don't
notice
the effect. What happens when you jump to another system in another part
of
the galaxy?
>
> Some more material to chew on...

Not really, I must say.

Greetings